11-Apr-17 2013 ISOE International ALARA Symposium JNES, Tokyo, JAPAN, 27-29 August,2013 Presentation on: Dose Reduction and Management during Overhauling of Reactor Coolant Pump at CHASHMA NPP-1 Delivered by: Makshoof A Mubbasher Manager HPD C-1 CHASHMA NUCLEAR POWER PLANT-1

Contents Mission Statement Plant Specific Information Dose Monitoring and Control in Plant Processes Dose Reduction during Overhauling of RCPs De-Contamination facility and scheme De-Contamination process Radiological Condition of RCPs [Pre & Post De-Cont.] Dose Management during Overhauling of RCPs Conclusion CHASHMA NUCLEAR POWER PLANT-1

1. Mission Statement To generate electricity in a demonstrably safe, reliable and cost effective manner over the long term for the benefit of our society and stake holders as well as to consolidate the basis for development of the nuclear power industry in Pakistan. CHASHMA NUCLEAR POWER PLANT-1 C-1 C-2 3

2. Plant Specific Information 11-Apr-17 2. Plant Specific Information Construction started in 1992 Project Completion in 2000. RCA is divided into 5 Radiation Zones based on dose rate. 1st Criticality (3rd May 2000) Commercial Operation since 15th Sep. 2000. Cumulative Availability Factor is 76.7%, and in Cycle-9, it is 96.13% Cumulative Capacity Factor is 73.51%, and in Cycle-9, it is 93.1% 08 Refueling Outages till date 239 days continuous operation in cycle-8 Owner Pakistan Atomic Energy Commission (PAEC) Regulatory Regime of Pakistan Nuclear Regulatory Authority (PNRA) Supplier CZEC/China Designer SNERDI/China Rated Th. Power 998.6 MWth Gross Elec. Output 325 MWe 2 loop PWR light water reactor Fuel Assemblies -121, Enriched Uranium 3.4%. CHASHMA NUCLEAR POWER PLANT-1

3. Dose Monitoring and Control in Plant Processes Design Provisions Radiological status of the plant is monitored through Process, Area and Effluent Radiation Monitors , 30 APR, 63 AAR and 27 AER. On-line monitoring of reactor coolant dose rate (APR-021& 421) Purification system in downstream of Let-down HX Cat-ion/An-ion/Mixed-bed resin column Filter in SCV at up/down stream of mixed bed. Routine Operation Routine monitoring of reactor coolant activity Compliance with Tech Spec on coolant activity a) ≤ 1 µCi/g [Dose Equivalent I-131], and b) ≤ 100/E µCi/g [Gross radioactivity]. CHASHMA NUCLEAR POWER PLANT-1

Outage Preparation Oxidation Process Gas stripping function Radioactive Noble gases are removed during normal operation Pressurizer & VCT SGW for treatment Outage Preparation Oxidation Process The process is considered as dose reduction technique. The process involves removal of the magnetite layer (mostly Nix Fe3 O4) of corrosion products formed during power operation. Hydrogen peroxide (H2O2) is injected in the primary system. The corrosion products get detached from the system. The contaminants are removed through ion exchange column (mixed bed) and filter in SCV. RPV Head is opened when radionuclide concentration in SRC meets a certain criteria: Total  <4E9 Bq/m3 and/or Co-58 < 2E8 Bq/m3, Co-60 < 2E8 Bq/m3, I-131< 5E7 Bq/m3, Xe-133 < 1E8 Bq/m3 CHASHMA NUCLEAR POWER PLANT-1

Behavior of Coolant Activity during oxidation Process CHASHMA NUCLEAR POWER PLANT-1 Bq/m3

Dose Rate at Selected Points of Primary Loop CHASHMA NUCLEAR POWER PLANT-1

4. Dose Reduction during Overhauling of RCPs Chemical De-Contamination Facility RCP decontamination Sleeve / Impeller /studs De-Cont. Long tools decontamination The facility is equipped with followings: Main tank equipped with ultrasonic generator device Recirculation pump Electrical heaters Sampling system Reagent preparation as subsystem Liquid waste storage tanks It also provides space for overhaul of Pump & Motor CHASHMA NUCLEAR POWER PLANT-1

De-Cont. Scheme Chemical Addition Alkaline Permanganate Citric Acid + Oxalic Acid Flushing Water De-Cont . Tank + US Generator Electric Heater SLW Process Drain Hold up Tank Liquid Waste Hold up Tank Temp Control pH Control CHASHMA NUCLEAR POWER PLANT-1

De-Contamination Process [AP-CITROX] AP-CITROX , a proven De-Cont. method was applied. Following were salient features of the process. work piece is kept at 90-95 °C in AP Solution [alkaline + KMnO4 ] for a certain time, followed by rinsing with Demineralized Water (DMW). work piece is kept at 90-95 °C in CITROX Solution [Citric Acid + Oxalic Acid ] + Corrosion inhibitor + EDTA for certain time, followed by rinsing with DMW. work piece is made passive by use of H2O2 at 60 °C in an acidic medium for certain time, followed by rinsing with DMW. CHASHMA NUCLEAR POWER PLANT-1

Total Activity Leached out from RCP; Total 158 GBq (~4 Ci) removed. Nuclide leached out were mainly Mn-54, Cr-51, Co-58, Co-60, Zr-95, Nb-95, Sb-124, Mo-99, Fe-59 & Sn-113. The isotopes having maximum activity were Co-60, Co-58 & Cr-51. Dose rates at the surface of RCP for different selected points were < 1mSv/h (except hot spot). Liquid Waste Produced Maximum liquid waste generated in De-Cont. process of RCP was 60 m3. CHASHMA NUCLEAR POWER PLANT-1

5. Radiological Condition of RCPs Pre De-Cont. Survey data Outage RFO-6 RFO-7 RCPs RCP-B RCP-A Survey Points mSv/h Pt.1 113 50 Pt.2 145 Pt.3 92 66 Pt.4 48 40 Pt.5 35 Pt.6 28 CHASHMA NUCLEAR POWER PLANT-1

Post De-Cont. Survey data and Dose Reduction Factor (DRF) Outage RFO-6 RFO-7 RCPs RCP-B DRF RCP-A Survey Points mSv/h Pt.1 11 10.27 20 2.5 Pt.2 58 Pt.3 3 30.7 2 33 Pt.4 24 5 8 Pt.5 1 50 35 Pt.6 28 4 7 DRF Range 11~50 2.5~58 Ave. DRF 27 CHASHMA NUCLEAR POWER PLANT-1

6. Dose Management during Overhauling ALARA procedure developed for overhauling; Procedure developed jointly by Maintenance and RP, considering all important steps of overhauling, number of personnel involved and estimated time of each overhauling step. Maintenance, ISI and RP Teams Formation 03 Maintenance teams each composed of 07 personnel were formed to perform overhauling tasks. 02 personnel supervised the job. Besides this, 01 ISI team composed of 05 personnel conducted inspection of various components of RCP. 02 RP teams were formed each composed of 03 personnel to perform the survey, look after dosimetery requirement and personnel protection during the overhauling. CHASHMA NUCLEAR POWER PLANT-1

Use of removable shielding to reduce exposure On Hand Training Organized by Maintenance Division and RP Practice on various steps of overhauling Use of protective Use of shielding Time management and control Use of removable shielding to reduce exposure Portable lead plates (6mm) Portable lead blanket (5mm) Lead Gloves (3mm) Lead Apron (3mm) Establishing collective dose(CD) targets Considering the job scope, personnel involved and expected time, collective dose were estimated. Following is the comparison of estimated & actual CD along with maximum personal dose. CHASHMA NUCLEAR POWER PLANT-1

RCP Overhauling Steps CHASHMA NUCLEAR POWER PLANT-1 (work on shroud )

RCP Overhauling Steps CHASHMA NUCLEAR POWER PLANT-1 (work on Impeller)

7. Conclusion Dose Reduction Factor (DRF) Dose Management AP-CITROX was successfully applied. Following were achieved: Radioactivity removed =158 GBq (~4 Ci) Average DRF achieved = 24 Maxi DRF =58 Dose Management Target CD were carefully estimated. In case of RCP-B overhauling, the actual CD was in close agreement with the target CD while for RCP-A it was well below the target CD. Thus principle of optimization of protection was successfully implemented. However, further improvement in reducing the worker doses can be made with application of technologically advance maintenance tools and improving the De-Cont. processes. CHASHMA NUCLEAR POWER PLANT-1

Questions CHASHMA NUCLEAR POWER PLANT-1

thanks & appreciations for patience and attention 11-Apr-17 CHASHMA NUCLEAR POWER PLANT-1 thanks & appreciations for patience and attention